The present invention relates to an automatically shifted layshaft transmission, and more particularly to a method for making adjustments to a synchronizer actuation mechanism in such a transmission.
Some automatically shifting transmissions employ dual clutches and layshafts. For each of the two layshafts, an electric motor rotates a shift drum through various positions, causing shift forks to actuate synchronizers attached to the corresponding gearing. When the shift drum is in an appropriate position, the layshafts may carry torque through the application of a corresponding automatically actuated clutch.
In order to increase shifting speed and decrease transmission noise it is important to know at what shift drum rotation angle the synchronizer begins to transfer torque. Unfortunately, the typical transmission tolerance stack-up may have a relatively large tolerance band around the expected position. This makes increases in shifting speed and decreases in noise difficult.
As a result, some have tried to apply an adaptive algorithm to account for the tolerances, but such algorithms tend to be slow and exhibit larger than desired variability. One adaptive algorithm uses the change in speed across the synchronizer during shifts to infer the shift drum position where torque capacity is achieved. However, such an approach is susceptible to noise factors such as road conditions, driving styles and part-to-part variability. Also, since the speed change across a synchronizer is strongly influenced by the overall control of the transmission, any design change may require a time-intensive recalibration of the adaptive routine as well.